Circuits for the amplification of electric oscillation



Sept. 26, 1939. J. VAN DER MARK El AL 2,173,910

CIRCUITS FOR THE AMPLIFICATIQN ELECTRIC OSCILLATION Filed July 18, 1956fly I 2 i in. 5 a -L -L F \NVENTORS JAN VAN DER MARK GERRH vmes ATTQRNEYPatented Sept. 26, 1939 PATENT OFFICE CIRCUITS FOR THE AMPLIFICATION OFELECTRIC OSCILLATION Jan van der Mark and Gerrit de Vries, Eindhoven,Netherlands, assignors to N. V. Philips Gloeilampenfabrieken,

Eindhoven,

Netherlands. a

corporation of the Netherlands Application July 18, 1936,. Serial No.91,274 In the Netherlands August 9, 1935 '7 Claims.

This invention relates to a circuit arrangement for the amplification ofelectric oscillations in which use is made of amplifier valves having anegative plate voltage and is an improvement in or modification of thecircuit arrangement described and claimed in application, Ser. No.39,094, filed Sept. 4, 1935, which has issued as Patent 2,094,477 and isassigned to the same assignee as the present application. Theoscillations to be amplified are impressed upon the control grid andbring about a variable space charge adjacent the plate electrode. Thisvariable space charge induces a variable charge on the plate which givesrise to a plate current of the same frequency as that of theoscillations impressed on the control grid. The plate current has inaddition the property that the amplitude increases proportionally to thefrequency of the oscillation and is displaced in phase by 90 relativelyto the grid alternating voltage. When the amplified alternating voltageoccurs in the plate circuit across a resistance in the plate circuit,this amplified alternating voltage will therefore increaseproportionally to the frequency with otherwise constant grid alternatingvoltage. The amplification is consequently dependent upon frequency.This is disadvantageous because in the majority of cases amplificationindependent of frequency is required.

According to the invention, amplification independent of frequency isobtained by the plate circuit including an impedance having a primarilycapacitative behavior.

The operation of the arrangment according to the invention will beappreciated by the fact that a current having a constant amplitude setsup across an condenser a voltage decreasing with the frequency.

W'hen consequently the amplitude of the our- 40 rent increasesproportionally to the frequency, as

is the case with amplifier valves having a negative plate voltage, thevoltage across the condenser will be independent of the frequency.

Fig. 1 shows a circuit arrangement for obtaining amplificationindependent of frequency in accordance with the invention.

Fig. 2 shows a circuit similar to Fig. 1 but employing reaction toreduce the apparent input capacity of one of the valves.

The circuit according to the invention is shown in Fig. 1 of theaccompanying drawing. It comprises, for example, two cascade-connectedscreen grid valves l and 2 having a negative plate voltage which issupplied by a source of voltage Ea through resistances 3 and 4respectively. The

plate circuit of each amplifier valve includes in addition a condenser 5and 6 respectively. The resistances 3 and 4 have such a value that theplate impedance is governed almost exclusively by the condensers 5 and 6so that amplification 5 independent of frequency is obtained. Since theamplification is higher according as the condensers 5 and 6 are reduced,it may be desirable, particularly in the case of amplification ofoscillations of very high frequency, that the condensers 5 and B shouldbe omitted and that the natural capacity of the amplifier valves betweenthe plate and the cathode and between the control grid and the cathodeshould be put up with. If even this capacity is still too high, it maybe reduced, 5 for example in the case of amplifier circuits comprisingthree cascade-connected valves, by providing as shown in Fig. 2 forcapacitive reaction, such as by the condenser I, from the plate circuitof the third valve to the grid circuit of the second valve, whichensures a decrease of the apparent capacity between the control grid andthe cathode of the second valve.

What we claim is:

1. A circuit for the uniform amplification of electric oscillationsindependent of frequency, comprising an electron discharge tube providedwith cathode, grid and plate electrodes an input circuit connectedbetween cathode and grid, and an output circuit connected betweencathode and 30 plate electrode, said plate electrode being supplied witha negative operating potential with respect to the cathode, and animpedance included in said plate circuit for rendering said circuitprimarily capacitative.

2. A circuit for the amplication of electric oscillations, comprising avacuum tube provided with cathode, grid and plate electrodes, an inputcircuit connected between cathode and grid, an output circuit connectedbetween cathode and 0 plate, a source of potential included in saidoutput circuit for impressing a negative potential with respect to thecathode on the plate electrode, and a resistance and a shunt capacityalso included in said output circuit. 45

3. A circuit for the amplification of electric oscillations, comprisinga vacuum tube provided with a cathode, a control grid, a screen grid anda plate electrode, an input circuit connected between cathode andcontrol grid, an output circuit 50 connected between cathode and plateelectrode, a source of potential included in said output circuit forimpressing a negative potential with respect to the cathode on the plateelectrode, means for impressing a positive potential on said screen 55grid, and a resistance and a shunt capacity also included in said outputcircuit.

4. A circuit for the amplification of electric oscillations comprising aplurality of vacuum tubes connected in cascade, each provided withcathode, grid and plate electrodes, an input circuit connected betweenthe cathode and grid of the first tube, each tube having an outputcircuit which includes a source of potential for impressing a negativepotential with respect to the cathode on the plate electrode, aresistance and a shunt condenser, the grid of each succeeding tube beingdirectly coupled to the output circuit of the one preceding.

5. A circuit for the amplification of electric oscillations comprising aplurality of vacuum tubes connected in cascade, each provided withcathode, grid and plate electrodes, an input circuit connected betweenthe cathode and grid of the first tube, each tube having an outputcircuit which includes a source of potential for impressing a negativepotential with respect to the cathode on the plate electrode, the gridof each succeeding tube being directly coupled to the output circuit ofthe one preceding, and a condenser connected between the plate of onetube and the grid of the preceding tube.

6. A circuit for the amplification of electric oscillations comprising aplurality of vacuum tubes connected in cascade, each provided with acathode, a control grid, a screen grid and a plate electrode, an inputcircuit connected between the cathode and the control grid of the firsttube, each tube having an output circuit which includes a source ofpotential for impressing a negative potential with respect to thecathode on the plate electrode a series resistance and a shuntcondenser,the grid of each succeeding tube being coupledto the outputcircuit of the one preceding, and means for impressing a positivepotential on each of said screen grids.

7. A circuit for the amplification of electric oscillations according toclaim 6 wherein a condenser is connected between the plate electrode ofone tube and the control grid of the preceding tube.

JAN VAN DER MARK. GERRIT DE VRIES.

